Leveling boat lift

ABSTRACT

A boat lift has a boat cradle mounted on a top side of a lift. Wheels are attached to the lift frame, and vertically oriented extendable legs are attached to the lift frame and configured such that with each leg retracted to a fully retracted position the lift frame is supported on the wheels. A leg controller is operative, in a leveling mode, to extend or retract each leg independently to position bottom ends of the legs at different vertical positions on an uneven lake floor as required to support the lift frame in a horizontal orientation with the wheels raised above the lake floor, and is operative in a lifting mode to extend or retract all legs simultaneously to move the lift frame up or down while maintaining the lift frame in the horizontal orientation.

This invention is in the field of elevating equipment and in particular a boat lift for raising a boat for storage above the surface of a water body.

BACKGROUND

Boat lifts are used to raise boats above the water surface of a lake or like body of water for storage such that the boat is not contacted and moved about by waves during inclement weather. Typically such lifts are used with small recreational boats where the operator wishes to store the boat in a position where same is quickly ready for use when desired, but is also safe from stormy water, especially when left un-attended for longer periods of time.

Such boat lifts typically comprise a frame mounted on legs that support the frame on the bottom floor of the lake. The frame has a cradle on its top side and is lowered so the boat can be maneuvered above the cradle, and then the frame is raised and the cradle engages the bottom of the boat and raises the boat above the water surface.

U.S. Pat. No. 4,773,346 to Blanding discloses a boat lift with a vertical hydraulic cylinder attached at each corner of a rectangular frame with a boat cradle on a top side thereof The piston of each hydraulic cylinder extends downward to form a leg to support the frame. An adjustable leg extension at the bottom end of each piston is moved up or down as required and then locked to support the frame in a horizontal orientation on a sloping or uneven lake floor where each leg will need to be a different length. Once the leg extensions have been adjusted to level the frame, pressurized water is directed to the hydraulic cylinders so same are activated simultaneously such that each piston moves up or down the same distance to thereby move the frame up and down while maintaining the horizontal orientation.

U.S. Pat. No. 5,380,143 to Mohan discloses a combination boat trailer and boat lift where the trailer, with the boat secured to the trailer, is backed into the water and disconnected from the towing vehicle. The boat is maneuvered to place the trailer in a desired location, such as adjacent to a dock, and then a winch is activated to move legs downward simultaneously against the floor of the lake and raise the trailer and attached boat up above the water.

Similarly U.S. Pat. No. 6,257,167 to Joaquim discloses a combination boat trailer and boat lift where a separate upper frame is mounted to the top of a base frame that is mounted on wheels. The base frame is placed at the desired location in the water and adjustable legs are moved down against the lake floor to support the base frame. The upper frame is then moved up to lift the boat above the surface of the water.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a boat lift that overcomes problems in the prior art.

In a first embodiment the present invention provides a boat lift apparatus comprising a lift frame and a boat cradle mounted on a top side of the lift frame and configured to support a boat. A plurality of wheels are attached to the lift frame, and a plurality of vertically oriented extendable legs are attached to the lift frame and configured such that with each leg retracted to a fully retracted position the lift frame is supported on the wheels for movement along the ground by a tow vehicle connected to the lift frame. A leg controller is operative, in a leveling mode, to extend or retract each leg independently to position bottom ends of the legs at different vertical positions on an uneven lake floor as required to support the lift frame in a substantially horizontal orientation with the wheels raised above the lake floor, and is operative in a lifting mode to extend or retract all legs simultaneously to move the lift frame up or down while maintaining the lift frame in the substantially horizontal orientation.

In a second embodiment the present invention provides a method of raising a boat above a surface of a lake for storage. The method comprises mounting a boat cradle on a top side of a lift frame and configuring the boat cradle to support the boat; mounting a plurality of wheels to the lift frame; attaching a plurality of vertically oriented extendable legs to the lift frame and retracting each leg to a fully retracted position such that the lift frame is supported on the wheels, and connecting a tow vehicle to the lift frame; maneuvering the tow vehicle to place the lift frame in a desired position in the lake with the wheels resting on an uneven lake floor of the lake, and disconnecting the tow vehicle; with a leg controller in a leveling mode, extending or retracting each leg independently to position bottom ends of the legs at different vertical positions on the uneven lake floor as required to support the lift frame in a substantially horizontal orientation with the wheels raised above the lake floor; with the leg controller in a lifting mode, extending or retracting all legs simultaneously to move the lift frame up or down as required to position the boat cradle below the surface of the lake while maintaining the lift frame in the substantially horizontal orientation; maneuvering the boat to float on the surface of the lake above the boat cradle; and with the leg controller in the lifting mode, extending all legs simultaneously to move the lift frame up and raise the boat above the surface of the lake while maintaining the lift frame in the substantially horizontal orientation.

Thus it is not required to go under the water to manually move leg extensions or other leveling devices to level the lift frame so the boat can be supported in a stable level orientation.

DESCRIPTION OF THE DRAWINGS

While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:

FIG. 1 is a schematic top view of an embodiment of a boat lift apparatus of the present invention;

FIG. 2 is a front view of the embodiment of FIG. 1 with the extendable legs in the fully retracted position;

FIG. 3 is a front view of the embodiment of FIG. 1 with the extendable legs at different vertical positions on an uneven lake floor supporting the lift frame and boat cradle in a horizontal orientation with the boat cradle below the surface of the water, and with a boat floating above the boat cradle;

FIG. 4 is a side view of the embodiment of FIG. 1 in the position of FIG. 3;

FIG. 5 is a front view of the embodiment of FIG. 1 with the extendable legs at different vertical positions on an uneven lake floor supporting the lift frame and boat cradle in a horizontal orientation with the boat cradle and boat raised above the surface of the water;

FIG. 6 is a side view of the embodiment of FIG. 1 in the position of FIG. 5;

FIG. 7 is front view of an extendable leg for use with the boat lift apparatus of FIG. 1 where the lift frame is supported at a first height above the lake floor with the hydraulic cylinder in a first position;

FIG. 8 is a front view of the extendable leg of FIG. 7 where the lift frame is supported at an increased second height above the lake floor with the hydraulic cylinder in the same first position as in FIG. 7;

FIG. 9 is a side view of the extendable leg of FIG. 7 in the position of FIG. 8;

FIG. 10 is a schematic view of the extendable leg of FIG. 7 with the hydraulic cylinder in a fully extended position;

FIG. 11 is a schematic view of the extendable leg of FIG. 7 with the hydraulic cylinder in a fully retracted position.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIGS. 1-6 schematically illustrate an embodiment of a boat lift apparatus 1 of the present invention. The apparatus 1 comprises a lift frame 3 and a boat cradle 5 mounted on a top side of the lift frame 3. The boat cradle 5 is configured to support a boat 7 and includes curved support members 9 that are spaced apart on the lift frame 3 such that the weight of the boat 7 may be carried on the support members 9 without damaging the boat 7. A pair of wheels 11 and a hitch 13 are attached to the lift frame 3.

A plurality of vertically oriented extendable legs 15 are attached to the lift frame 3 and configured such that with each leg 15 retracted to a fully retracted position, as illustrated in FIG. 2, the lift frame 3 is supported on the wheels 11 for movement along the ground by a tow vehicle connected to the hitch 13. In the illustrated apparatus 1 there are four extendable legs 15, each leg 15 attached in proximity to a corner of a substantially rectangular lift frame 3. It is contemplated that other configurations could perform the function as well, such as providing more legs for a heavier boat.

In the illustrated apparatus 1, each leg 15 comprises a hydraulic cylinder with a barrel 17 of the hydraulic cylinder attached to the lift frame 3, and a piston 19 of the hydraulic cylinder extending downward, and with a foot plate 21 on a bottom end of the piston 19. It is contemplated that extendable screws, jacks, or the like could be used as well to provide the extendable legs 15, however hydraulic cylinders using a hydraulic fluid such as oil, water, air, or the like are well suited to the required function.

A leg controller 23 is operative, in a leveling mode, to extend or retract each leg 15 independently to position the foot plates 21 on bottom ends of the legs 15 at different vertical positions on an uneven lake floor 25 as required to support the lift frame 3 in a substantially horizontal orientation with the wheels 11 raised above the lake floor 25, as shown in FIGS. 3 and 4. Thus for each hydraulic cylinder leg 15, the leg controller 23 is operative to selectively control a flow of hydraulic fluid through conduits 27 to the barrel 17 to extend the piston 19, to retract the piston 19, and to lock the piston 19 in a fixed position relative to the barrel 17.

Manipulating the legs 15 with the leg controller 23 in the leveling mode allows the operator to level the lift frame 3, and then with the leg controller 23 in a lifting mode, the leg controller is operative to extend or retract all legs 15 simultaneously to move the lift frame 13 up or down while maintaining the lift frame 13 in the substantially horizontal orientation. Thus when the leg controller 23 is in the lifting mode, the flow of hydraulic fluid to the barrel 17 of each hydraulic cylinder leg 15 is the same, and the lift frame thus moves up and down maintaining the horizontal orientation.

FIGS. 7-11 schematically illustrate a convenient configuration of an extendable leg 15′ for use with the boat lift apparatus 1. The leg 15′ comprises an inner tube 33 telescoping inside an outer tube 35, and an extendable actuator, provided by hydraulic cylinder 37, operative to extend the inner tube 33 to a fully extended position with respect to the outer tube 35, as illustrated in FIG. 10, and to retract the inner tube 33 to a fully retracted position with respect to the outer tube 35, as illustrated in FIG. 11.

The hydraulic cylinder 37 is mounted inside the tubes vertically oriented tubes 33, 35. A barrel pin 39 connects the top of the barrel 17′ of the hydraulic cylinder 37 to the outer tube 35 and the piston 19′ of the hydraulic cylinder extends downward, and is connected at a lower end thereof to the inner tube 33 by a piston pin 41. Thus extending and retracting the hydraulic cylinder 37 extends and retracts the inner tube 33 with respect to the outer tube 35. The lift frame 3′ is attached to the outer tube 35, and a foot plate 21′ on the bottom end of the inner tube 33 supports the leg 15′ on a lake floor.

The hydraulic cylinder 37 is attachable to the outer tube 35 at a plurality of locations such that a length L of the extendable leg 15′ can be adjusted. The outer tube 35 defines a plurality of vertically spaced barrel holes 43. In FIG. 7, the barrel pin 39 is inserted in the top barrel hole 43A such that the leg 15′ has a length L and the lift frame 3′ is supported at a height H above the lake floor at the footplate 21′. In FIG. 8, the barrel pin 39 is inserted in a lower barrel hole 43B such that the leg 15′ has an increased length L′, with the hydraulic cylinder 37 at the same extension that shown in FIG. 7, and the lift frame 3′ is supported at an increased height H′ above the lake floor. Thus the extendable leg 15′ provides an increased range of possible support heights for the lift frame 3′ compared to simply mounting the hydraulic cylinder 37 directly to the lift frame, and so can be used in a wider range of water depths.

If a hydraulic seal, hose, or valve fails, the hydraulic cylinder 37 will retract and the lift frame 3′ will fall down. With even a small leak, the hydraulic cylinder 37 can creep down over extended periods of time. A typical boat lift will often be unattended for extended periods, and so the extendable leg 15′ also comprises a stop mechanism operative to prevent the inner tube 33 from retracting into the outer tube 35 to prevent the lift frame 3′ from moving downward. A stop pin 45 can be inserted into any one of a plurality of vertically spaced stop holes 47 defined by the outer tube 35 above the top end of the inner tube. With the stop pin 45 inserted as shown in FIG. 8, the outer tube can only move downward until the stop pin contacts the top end 49 of the inner tube 33. With the plurality of stop holes 47, the stop mechanism can be adjusted to support the lift frame 3′ at any one of a plurality of vertical locations as may be required.

The present invention thus provides a method of raising a boat 7 above a surface 29 of a lake for storage above the water and out of reach of damaging waves. The method comprises mounting a boat cradle 5 on a top side of a lift frame 3 and adapting the boat cradle 3 to support the boat 7, mounting a plurality of wheels 11 to the lift frame 3, and attaching a plurality of vertically oriented extendable legs 15 to the lift frame 3 and retracting each leg 15 to a fully retracted position such that the lift frame 3 is supported on the wheels 11 as shown in FIG. 2. A tow vehicle 31 is connected to the lift frame 3 at hitch and maneuvered to place the lift frame 3 in a desired position in the lake with the wheels 11 resting on an uneven lake floor 25 of the lake, and then the tow vehicle 31 is disconnected.

With the leg controller 23 in the leveling mode, each leg 15 is extended or retracted independently to position the foot plates 21 on bottom ends of the legs 15 at different vertical positions on the uneven lake floor 25 as required to support the lift frame 3 in a substantially horizontal orientation with the wheels 11 raised above the lake floor 25, as shown in FIGS. 3 and 4. Then with the leg controller 23 in the lifting mode, all legs 15 are extended or retracted simultaneously to move the lift frame 3 up or down as required to position the boat cradle 5 below the surface 29 of the lake while maintaining the lift frame 3 in the substantially horizontal orientation. Barrel pins 39 can be inserted in barrel holes 43 selected to suit water depth in the location of use.

The boat 7 is maneuvered to float on the surface 29 of the lake above the boat cradle 5, and with the leg controller 23 in the lifting mode, all legs 15 are extended simultaneously to move the lift frame 3 up and raise the boat 7 above the surface 29 of the lake while maintaining the lift frame 3 in the substantially horizontal orientation, as shown in FIGS. 5 and 6. Stop pins 45 can be inserted in stop holes 47 to prevent the boat from moving downward.

Thus the present invention allows for fast placement and leveling of a boat lift on an uneven lake floor without the need to manually manipulate leg extensions or other leveling devices under the water.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention. 

1. A boat lift apparatus comprising: a lift frame and a boat cradle mounted on a top side of the lift frame and configured to support a boat; a plurality of wheels attached to the lift frame; a plurality of vertically oriented extendable legs attached to the lift frame and configured such that with each leg retracted to a fully retracted position the lift frame is supported on the wheels for movement along the ground by a tow vehicle connected to the lift frame; a leg controller operative, in a leveling mode, to extend or retract each leg independently to position bottom ends of the legs at different vertical positions on an uneven lake floor as required to support the lift frame in a substantially horizontal orientation with the wheels raised above the lake floor; and wherein the leg controller is operative in a lifting mode to extend or retract all legs simultaneously to move the lift frame up or down while maintaining the lift frame in the substantially horizontal orientation.
 2. The apparatus of claim 1 wherein at least one leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward.
 3. The apparatus of claim 2 further comprising a foot plate on a bottom end of the piston.
 4. The apparatus of claim 1 wherein each leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward.
 5. The apparatus of claim 4 wherein, for each hydraulic cylinder, the leg controller is operative to selectively control a flow of hydraulic fluid to the barrel to extend the piston, to retract the piston, and to lock the piston in a fixed position relative to the barrel.
 6. The apparatus of claim 5 wherein when the leg controller is in the lifting mode, the flow of hydraulic fluid to each hydraulic cylinder is substantially the same.
 7. The apparatus of claim 6 comprising four legs, each leg attached in proximity to a corner of a substantially rectangular lift frame.
 8. The apparatus of claim 1 wherein at least one extendable leg comprises an inner tube telescoping inside an outer tube, and an extendable actuator operative to extend the inner tube to a fully extended position with respect to the outer tube, and to retract the inner tube to a fully retracted position with respect to the outer tube; and wherein the extendable actuator is attachable to one of the inner and outer tubes at a plurality of locations such that a length of the at least one extendable leg can be adjusted.
 9. The apparatus of claim 8 wherein the at least one extendable leg comprises a stop mechanism operative to prevent the inner tube from retracting into the outer tube to prevent the lift frame from moving downward.
 10. The apparatus of claim 9 wherein the stop mechanism can be adjusted to support the lift frame at a plurality of vertical locations.
 11. A method of raising a boat above a surface of a lake for storage, the method comprising: mounting a boat cradle on a top side of a lift frame and configuring the boat cradle to support the boat; mounting a plurality of wheels to the lift frame; attaching a plurality of vertically oriented extendable legs to the lift frame and retracting each leg to a fully retracted position such that the lift frame is supported on the wheels, and connecting a tow vehicle to the lift frame; maneuvering the tow vehicle to place the lift frame in a desired position in the lake with the wheels resting on an uneven lake floor of the lake, and disconnecting the tow vehicle; with a leg controller in a leveling mode, extending or retracting each leg independently to position bottom ends of the legs at different vertical positions on the uneven lake floor as required to support the lift frame in a substantially horizontal orientation with the wheels raised above the lake floor; with the leg controller in a lifting mode, extending or retracting all legs simultaneously to move the lift frame up or down as required to position the boat cradle below the surface of the lake while maintaining the lift frame in the substantially horizontal orientation; maneuvering the boat to float on the surface of the lake above the boat cradle; and with the leg controller in the lifting mode, extending all legs simultaneously to move the lift frame up and raise the boat above the surface of the lake while maintaining the lift frame in the substantially horizontal orientation.
 12. The method of claim 11 wherein at least one leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward.
 13. The method of claim 12 further comprising a foot plate on a bottom end of the piston.
 14. The method of claim 11 comprising front right and left legs and rear right and left legs, and wherein each leg comprises a hydraulic cylinder with a barrel of the hydraulic cylinder attached to the lift frame, and a piston of the hydraulic cylinder extending downward.
 15. The method of claim 14 wherein, for each hydraulic cylinder, the leg controller is operative to selectively control a flow of hydraulic fluid to the barrel to extend the piston, to retract the piston, and to lock the piston in a fixed position relative to the barrel.
 16. The method of claim 15 wherein when the leg controller is in the lifting mode, the flow of hydraulic fluid to each hydraulic cylinder is substantially the same.
 17. The method of claim 16 wherein the lift frame is substantially rectangular and comprising attaching a leg in proximity to each corner of the lift frame.
 18. The method of claim 11 wherein at least one extendable leg comprises an inner tube telescoping inside an outer tube, and an extendable actuator operative to extend the inner tube to a fully extended position with respect to the outer tube, and to retract the inner tube to a fully retracted position with respect to the outer tube; and wherein the extendable actuator is attachable to one of the inner and outer tubes at a plurality of locations such that a length of the at least one extendable leg can be adjusted.
 19. The method of claim 18 wherein the at least one extendable leg comprises a stop mechanism operative to prevent the inner tube from retracting into the outer tube to prevent the lift frame from moving downward.
 20. The method of claim 19 wherein the stop mechanism can be adjusted to support the lift frame at a plurality of vertical locations. 